Battery Basics

Introduction

As battery powered device increasing in ubiquity, system EE need to have solid understand of battery chemistry, capacity, aging, and charging and discharged curve.

Overview

  • Chemistry
    • Lithium ion/LIPO/Lithium Polymer - Rechargeable
      • Operating voltage: ~ 3V to 4.2V
    • Alkaline
      • Operating voltage: 0.9V to 1.5V
    • Nickel–cadmium battery (NiCD)
      • 1.2V nominal
    • Nickel-Metal Hydride (NiMH)
      • 1.2V nominal
  • Capacity (measured in mAh)
    • Lithium ion
      • ~ 3000 mAh for a typical phone
    • Alkaline
      • ~1000 mAh for AAA battery
    • Nickel–cadmium battery (NiCD)
      • 1000 mAh
    • Nickel-Metal Hydride (NiMH)
      • 2500 - 2700 mAh
  • Energy Density
    • Volume Metric Density (measured in W-HR/L)
      • Lithium Ion: 210
      • Nickel–cadmium battery (NiCD): 140
      • Nickel-Metal Hydride (NiMH) : 180
  • Charging Rate
    • Measured in C
      • 1 C means it takes an hour to finish chaging from 0% to 100%; 2C means it takes 30 mins to finish charging.
  • Charging Curve
    • Lithum ion
      • Trickle charging -> Constant Current -> Constant Voltage -> Charging termination
        • termination is based on charging current falling below a threshold rate, typically 0.02C to 0.07C
    • Nickel-Metal Hydride (NiMH)
      • Trickle charging -> Constant Current -> top-off charge -> Charging termination

Q&A

Why is Lithium Ion battery chosen for premium portable electronics such as a smart phone?

    • Lithium Ion battery has the highest energy density.

References and Further Reading:

" Recharging Alkaline Batteries : Fact or Fiction?", https://zbattery.com/Recharging-Alkaline-Batteries-Fact-or-Fiction

"Battery Energy Density": https://forum.digikey.com/t/battery-energy-density/445?utm_adgroup=Battery%20Products&utm_source=google&utm_medium=cpc&utm_campaign=Dynamic%20Search_RLSA_Buyers&utm_term=&utm_content=Battery%20Products&gclid=CjwKCAjwjqT5BRAPEiwAJlBuBdy6wksR42v3cfwgH-gFmsifrNk9z1xg_K82YEDWmiR_GsrXdBnqmhoCfDoQAvD_BwE

"Battery Charging", https://www.ti.com/lit/an/snva557/snva557.pdf?ts=1596610924925&ref_url=https%253A%252F%252Fwww.google.com%252F

"Charging Lithium-ion", https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries#:~:text=Figure%203:Volts/capacity%20vs.%20time%20when%20charging%20lithium-ion.%20The%20capacity%20trails

"Developing Affordable Mixed Signal power ysstems for Battery Charger Applications", http://www.rusmagnet.ru/2019/MANUALS/en027883.pdf